1. Field of the Invention
The invention relates to a method and a device for grinding or cutting a workpiece, whereby a relative movement between the workpiece and the abrasive body, which consists of abrasive grain, binder material and fillers in some cases, takes place.
2. Description of the Prior Art
Abrasive bodies generally comprise three components. First, the cutting abrasive grain, which is, for example, corundum or silicon carbide, second, the binder material, which may be a resin but also a ceramic composition, and third, the filler.
The present invention exclusively relates to active fillers The effects of active fillers are commonly categorized into the following three major groups:
1. Decrease in the friction between abrasive grain, workpiece and chips, i.e. the fillers and their by-products must have the effect of high temperature lubricants or high pressure lubricants. They can thereby form a primary lubricating film of melted mass (e.g. cryolite) or a solid lubricating film (graphite, molybdenum sulfide, lead oxide). Secondary films may also be formed: metallic chloride (-sulfide) as a filler chlorine- (sulfur-) -separation metallic chloride (-sulfide) of the gound material. PA0 2. Protective effect by forming primary or secondary surface films on the abrasive grain, workpiece and chips (analogous to item 1). Grain destruction due to diffusion processes (e.g. spinel formation when grinding iron material containing corundum), welding of the grit to the grain or to the workpiece are thereby avoided. PA0 3. Cooling effects in the microrange due to height melting-, vaporization- and phase change temperatures and thermal phase change points which are favorable with respect to temperature. PA0 1. The amount of the active materials (fillers in a conventional disk) becomes independent of the volume triangle, i.e. any desired amount of active filler can be used. The volume triangle comprises three components, abrasive grain, binder and filler, which make together 100% of the disk volume. This means that any increase in one of the components neccessarily results in a reduction in one of the other components. This interaction is obviated by means of the method according to the invention, as the amount of the active materials is no longer in direct volume-depending relationship to the other components or actual components of the abrasive body. PA0 2. The mixing- and moulding problems occurring in the manufacture of abrasive disks are reduced by bonds containing low amounts or no fillers at all. PA0 3. The manufacture of solid bodies of or containing active materials, e.g. in the form of plates, is very simple. The dimensional and hardness tolerances can be chosen within a wide range, and the use of cheap resins is possible. PA0 4. Active liquids and hygroscopic fillers, i.e. active materials, can be encapsulated in porous bodies, which then form together a solid body.
Particularly active fillers are, for example, halegonides (e.g. lead chloride, fluorspar, cryolite etc.), chalegonides (e.g. pyrite, antimony sulfide, zinc sulfide, molybdenum sulfide selenides, tellurides etc.), low melting metals (e.g. lead, tin, low melting composition metals), or high pressure lubricants (e.g. graphite). In practice, lead chloride and antimony trisulfide have proved to the the best fillers with respect to service life and low temperature ("cool abrasion").
It has been found that a filler is more active the lower its phase change temperature (melting-, boiling, sublimation-, decomposition point) is. Due to the processing conditions in the manufacture of abrasive articles, these temperatures cannot fall below a certain value. Moreover, chemically highly active elements or compounds, e.g. chlorine, hydrogen chloride, sulfur, sulfur dioxide etc., should be set free in the grinding process during decomposition.
The problem arising with active fillers is such that in many cases fillers which are highly interesting in grinding techniques, i.e. highly effective, cause problems in the manufacture of the disk. Examples in this respect are hygroscopic fillers, for example. It is further to be considered that only a restricted amount of active fillers can be used in the abrasive disk or abrasive article as the abrasive grain and the binder material must also form a certain minimum amount in the abrasive disk.
Apart from the addition of active and cooling substances, for example, it is known to cool abrasive disks during the grinding process by means of liquid cooling agents, e.g. oil-water emulsion. When grinding at elevated circumferential velocities, for example, the liquid cooling agent is sprayed onto the abrasive disk by means of nozzles.